The purpose of the proposed work is to investigate various aspects of parotid acinar cell secretory activity in the adult rat by administering a chemical metabolic inhibitor which selectively effects the parotid acinar cells. Young rats are given daily injections of ethionine, a competitive inhibitor of methionine metabolism. Morphologic and biochemcial alterations are to be studied at the end of the intoxication period and during the immediate recovery period. Morphologic investigations will involve the following areas: 1. Morphologic appearance of the intoxicated gland; 2. Glandular recovery; 3. The nature of the crystalloid';. Biochemical studies will attempt to determine the compositon of: 1. The 'crystalloid'. 2. Secretory granules. Radioisotopic investigations will study: 1. The extent of acinar cell recovery from ethionine; 2. The mode of formation of the crystalloid; 3. The sites at which ethionine induced energy depletion inhibits the synthetic process.